[FFmpeg-cvslog] avcodec/snowdec: Fix integer overflow before htaps check

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Mon Jan 15 03:03:36 2018 +0100| [60bc7a6ec08a662c02e10eb1660d15e2a65ff0f5] | committer: Michael Niedermayer

avcodec/snowdec: Fix integer overflow before htaps check

Fixes: runtime error: signed integer overflow: -1094995529 * 2 cannot be represented in type 'int'
Fixes: 4828/clusterfuzz-testcase-minimized-5100849937252352

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 2eecf3cf8eeae67697934df326e98df2149881e5)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=60bc7a6ec08a662c02e10eb1660d15e2a65ff0f5
---

 libavcodec/snowdec.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index df425b8cf3..00fa064102 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -363,9 +363,10 @@ static int decode_header(SnowContext *s){
                 int htaps, i, sum=0;
                 Plane *p= &s->plane[plane_index];
                 p->diag_mc= get_rac(&s->c, s->header_state);
-                htaps= get_symbol(&s->c, s->header_state, 0)*2 + 2;
-                if((unsigned)htaps >= HTAPS_MAX || htaps==0)
+                htaps= get_symbol(&s->c, s->header_state, 0);
+                if((unsigned)htaps >= HTAPS_MAX/2 - 1)
                     return AVERROR_INVALIDDATA;
+                htaps = htaps*2 + 2;
                 p->htaps= htaps;
                 for(i= htaps/2; i; i--){
                     p->hcoeff[i]= get_symbol(&s->c, s->header_state, 0) * (1-2*(i&1));